Retrofitting Steam Boilers For Large Health Care Projects
Steam boilers are one of the most essential and critical components of a hospital central utility plant. Steam is essential for hospitals because it provides the most cost effective means of delivering building heating and steam for essential sterilization processes. Steam boilers in hospitals provide a myriad of uses, such as building heating, domestic hot water, steam laundry requirements, and steam for sterilization processes. The importance of steam boilers for hospital process is further confirmed by the Joint Commissioning requirement of N+1 for boilers in hospital central utility plants.
ASHRAE life expectancy of steam boilers is 35 years. Most healthcare facilities that I have surveyed consist of boilers that were over 35 years old, but in spite of their age, they were still operating and fulfilling the hospital steam requirements. Cleaver Brooks has conducted several surveys of hospitals and estimates that approximately 70% of the boilers that are installed in hospitals are more than 30 years old.
Steam boilers are often the last on the list of equipment to be replaced for the central utility plant in hospitals. This is because, unlike other equipment, steam boilers are usually maintained on a 24-hr basis and boiler mechanics often implement a great deal of preventative maintenance that extends the life of older steam boilers. Boilers can have all the tubes replaced, burners replaced or completely rebuilt in place, and these enhancements usually extend the service life beyond the ASHRAE life expectancy. However, this will not prevent the inevitable. At some point the boilers will need to be replaced. Boilers can be replaced for a number of reasons, but for hospitals, these are the most common reasons:
- They have reached end of their service life
- They are replaced because of a capital investment project
- They are no longer operational
- They are replaced as part of an energy upgrade
Replacing boilers for health care facilities provide many benefits to central utility plant operation; the newer boilers are more energy efficient, more sustainable, and more fuel-efficient than older boilers. Older boilers are often large, bulky, hard to operate, and difficult to maintain. The older boilers often take up to 90 minutes to heat up and therefore are often kept running to ensure that heating is available when required. Newer boilers can heat up as quickly as five minutes and can adjust to variable loads to reduce energy consumption.
Replacing boilers can be a huge capital cost, but making the right choice in the selection of new boilers can significantly impact the bottom line through decreased utility cost. There are also the added benefits of reducing boiler footprints, which can free up expensive real estate that can be used for other purposes. Local utility companies also provide incentives for boiler upgrades that can offset the initial capital cost.
Hospitals consume approximately 5% of the total energy used in the commercial sector1. The hospital industry spends more than $8 billion per year in energy cost1. More than 50% of the energy consumed derives from natural gas (Figure 1). The primary use of natural gas is for firing steam boilers to provide steam for sterilization, space heating, and water heating. Increasing the efficiency of the single piece of equipment with the highest natural gas use can provide a significant reduction in the cost of energy for a hospital.
What Should Be Considered When Looking At Steam Boiler Replacement?
There are some important factors that should be considered before boilers are replaced for a hospital central utility plant. Replacing a boiler plant can be a very expensive and tedious undertaking for the mechanical engineer, facility staff, and the mechanical contractor. Phasing considerations should be an integral part of the design and construction process. Replacing boilers usually means downtime or reduced capacity for the steam system and therefore the time of execution of these projects should be scheduled around periods of low-steam demand. A great deal of collaboration is necessary for all the stakeholders that will be involved in the boiler replacement project. The other important considerations are:
- Budget cost
- Right-sizing the boilers
- Environmental pollution
- Laundry requirements
- Sterile processing requirements
- Flue economizer
The initial cost of a boiler can be the smallest part of the overall boiler investment, followed by the maintenance and efficiency. A lower-efficiency boiler can obliterate the savings on initial budget cost savings in less than a year because of the high fuel use and inefficiencies. Because the steam boilers are used for so many services within the hospital, it is important to select the best boiler that suits its multiple process requirements.
However, all hospitals are becoming more aware and concerned with energy consumption, gas pricing, and operational efficiency. More and more facility engineers are turning to systems that not only address these issues but also those that can adapt and grow with the needs of their facility. Ultimately, when deciding to upgrade your boiler system, the key thing to look for is the long-term cost savings with regards to space, time, and energy.
Right-Sizing the Replacement Boilers
Due to the age of most boilers systems, the steam and hot water requirement may have changed over time and should be re-evaluated before boilers are replaced. It is a strong possibility that the existing boilers are too large, too small, or operate at the wrong temperature or pressure for the current heating or process requirements. Thorough and complete analysis of your steam and hot water usage is required before committing to a new or replacement boiler. This means the designer will have to work with the hospital to evaluate the steam pressure and volume needs; the daily, weekly, and annual cycle of boiler loads; and any special steam quality requirements. Boiler logs should be requested to fully understand the steam usage in the hospital.
There are some instances where there is a large steam requirement for the hospital for only part of the year. In these circumstances, the large boilers are being operated at low load (low efficiency) for the rest of the year for water heating or minimal demand applications. Often, large boilers cycle on and off during these low-load periods, further reducing the efficiency. For these situations the hospital should consider installing a small pony boiler, allowing the large main boilers to be shut down seasonally.
Climate change and environmental pollution is one of the most important agenda for developed countries. With the number of hospitals in operation in the USA, reducing the air pollution from boilers can be an important part of reducing environmental impact caused by boiler’s exhaust gases such as carbon monoxide, particulate matter, sulfur oxides, and nitrous oxide.
The Environmental Protection Agency (EPA) has strict mandates on boiler flue gas exhaust requirements. Most of the EPA regulations are based on the Clean Air Act enacted in 1963 and amended in subsequent years. Most state and local governments have defined specific requirements for regulating air pollution. It is important that the mechanical engineer understand the air pollution requirements for the AHJ and to ensure that they work with the boiler manufacturers to implement emission control technology if required.
Traditionally, laundry equipment in hospitals are steam-fired. This laundry equipment usually requires high-pressure or medium-pressure steam for operation. However, most hospitals are either consolidating their laundry services or totally outsourcing to reduce the operational cost associated with poor laundry management. For this reason, the current state of steam usage in hospitals is much lower. New boiler design should reflect the current hospital steam requirements.
Sterile Processing Requirements
The high temperature and penetrating power of steam makes it an ideal method of sterilization. A central sterile services department (CSSD) utilizes a large amount of steam for sterilizing equipment, medical devices, and other consumables for use in the operating rooms.
Some hospitals outsource these services and there is limited use for steam in these facilities. Hospitals that have low-steam requirements should consider the use of point of steam generators. Hospitals with low-steam requirements should also utilize condensing boilers for building heating and domestic hot water heating. Condensing boilers can operate at up to 98% efficiency compared to the max 83% average efficiency of steam boilers. Furthermore, hot water pipes are much easier to maintain than steam and condensate piping systems.
New larger steam boilers are averaging approximately 83% efficiency compared to 60% in units 30 years and older. It is estimated that 70% of the hospitals in the USA have steam boilers that are more than 30 years old. Because of the increase cost of operating a hospital, boiler replacements are sometime not a priority. Facilities engineers have to use innovative measures to improve the efficiency of the overall steam systems.
A common method of improving the efficiency of the boiler system is to implement stack economizers. Flue gases from boilers are typically between 450-650°F. The stack economizer can be used to recover some of this heat and used to pre-heat boiler makeup water used for domestic hot water heating. This installation requires downtime and should be scheduled around periods of low steam usage.
And condensate systems?
The conditioning of the steam and condensate piping should be assessed before boiler replacement projects. In order to reap the benefits of efficient boilers, the steam distribution systems should be well insulated and steam piping system in good shape. Uninsulated steam components result in large energy waste. Boiler replacement projects should be paired with steam pipe renovation projects in order to maximize the energy savings from the newer efficient boilers.
If Capital Cost Is Not Available, What Can Be Done?
If capital cost is not available the hospital facilities staff should implement a stringent preventative maintenance scheme to ensure improved performance and longer life. Boiler maintenance schemes should include cleaning and replacing metal parts such as water tubes, regular inspection of the metal casing for deterioration, and routine tune-up. A great intermediate alternative to a full boiler replacement is upgrading the burners, which warrants more discussion.
Upgrading Boiler Burners
In some cases, if the capital cost is not available, replacing the boiler burners would provide huge increases in efficiency for the boilers system. Local utilities will provide huge incentives to support boiler burner replacements.
New burners will provide improved turndown and firing rate. They are capable of producing 10 to 1 turndown. Older boilers that are more than 20 years old have far inferior turndown rates as low as 4 to 1. The newer burner uses a combination of VFDs to optimize fuel combustion.
Replacing boiler burners also reduces the ongoing maintenance requirements when compared to older burner systems. The reason for this is that the new controls allow for easier maintenance and tune-ups. Newer burners are much more sophisticated than older burner systems because they contain an electronic interface which makes it easy for facility staff to monitor and control the boilers.
Boiler burner replacement has the added benefits of reducing natural gas uses and combustion through energy efficiency improvements and lowering emissions rates of pollutants per unit of natural gas. Most new burners are equipped with oxygen trim controls that will reduce the carbon monoxide pollutants; this is done by operating the boiler burners at 5-10% excess oxygen.
Using oxygen trim controls also increases the efficiency of combustion because it allows less fuel to be consumed by the boilers. Newer burners utilize an internal recirculation path that reduces the nitrous oxide (NOx) emissions when compared to older burners. The new burners will improve air quality in communities surrounding the hospitals. The overall effect of burner replacement will reduce the facility’s carbon foot print.
Existing steam and condensate systems
The conditioning of the steam and condensate piping should be assessed before boiler replacement projects. In order to reap the benefits of efficient boilers, the steam distribution systems should be well insulated and steam piping system in good shape. Uninsulated steam components result in energy waste because they dissipate the heat into spaces that don’t require it. Boiler replacement projects should be paired with steam pipe renovation projects in order to maximize the energy savings from the boiler system. ES
1. Commercial Building Energy Alliance, 2012 Annual Report
2. The Boiler Book, Cleaver Brooks
3. The Joint Commission Standards
4. ASHRAE Owning and Operating Database